1. Field of the Invention
The present invention relates to a lifting structure which is provided on a dynamic electric machine and used when the machine is lifted.
2. Description of the Related Art
As shown in FIGS. 1 and 3, a dynamic electric machine has a stator frame 3 of a substantially circular cross-section. One end of the stator frame 3 is closed by an outer fan cover 1 and a terminal box 2 is provided on one side of the stator frame 3. Heat-radiating longitudinal ribs are formed on the outer surface of the stator frame 3 so as to extend in the axial direction of the stator frame 3. A lifting member 4 is fixed to the outer surface of the stator frame 3. The rotor shaft 6 of the motor projects outside from a mounting flange 5 which is provided on the end of the stator frame opposite to the outer fan cover 1. The lifting member 4 is an eye bolt in the illustrated case. The means for fixing the lifting member 4 includes a supporting portion 3A formed as a part of the stator frame 3 and having a threaded internal bore. The lifting member 4 has a threaded end portion which is screwed into the bore, whereby the fixing member 4 is fixed to the stator frame 3.
Thus, in the known arrangement described above, the position on the stator frame 3 to which the lifting member is connected is fixed. Therefore, when a geared motor 8 having a reduction gear 7 is coupled to the dynamic electric machine through the mounting flange 5 as shown in FIG. 2, since the weight of the reduction gear 7 largely varies depending on the reduction ratio, the position of the gravity center is largely moved to cause an unbalance of mass when the machine is lifted by, for example, a wire rope retained by the lifting member 4. Such a way of lifting is quite dangerous since the machine cannot be held stably. The position of the weight center also varies depending on whether the geared motor 8 is coupled to the mounting flange 5, with the result that a danger is often caused when lifting the machine with or without the geared motor 8.
In addition, the cost of the machine is raised due to the necessity for the formation of the threaded bore in the supporting portion of the stator frame.